C8953
NMR structural analysis - seminar
1D 13C-NMR
Jan Novotný
novotnyjan@mail.muni.cz
March 9, 2016
Diastereotopicity1
1
http://www.chem.wisc.edu/areas/reich/chem605/
Diastereotopicity1
1
http://www.chem.wisc.edu/areas/reich/chem605/
Determine the number of nonequivalent 1
H signals :
Determine the number of nonequivalent 1
H signals :
1
H vs 13
C NMR
1
H 13
C
Spin number 1
H: s=1
2
× 2
H: s=1 13
C: s=1
2
× 12
C: s=0
Abundance [%] 99.98 1.1
Gyromagnetic ratio [107
rad.T−1
.s−1
] 26.8 6.7
Chemical shift range [ppm] 0 - 15 0 - 200
Nuclear shielding σdia σdia + σpara
Integration of signals ×
T1 relaxation [s] 1-20 1-40
Homonuclear J-interaction ×
H↔C J-interaction (∼ 100-250 Hz) carbon satellites (n + 1) splitting × decoupling
1
H-13
Cα 1
H-13
Cβ
1
H-12
C
ωC-0.51
JHCωC+0.51
JHC
1
JHC
1
JHC
1D 1
H NMR
1D 13
C NMR
1
Hβ-13
C1
Hα-13
C
1
H decoupled
1
H vs 13
C NMR
1
H 13
C
Spin number 1
H: s=1
2
× 2
H: s=1 13
C: s=1
2
× 12
C: s=0
Abundance [%] 99.98 1.1
Gyromagnetic ratio [107
rad.T−1
.s−1
] 26.8 6.7
Chemical shift range [ppm] 0 - 15 0 - 200
Nuclear shielding σdia σdia + σpara
Integration of signals ×
T1 relaxation [s] 1-20 1-40
Homonuclear J-interaction ×
H↔C J-interaction (∼ 100-250 Hz) carbon satellites (n + 1) splitting × decoupling
Important regions of 13
C chemical shifts
Aldehydes RCH=O
Ketones R1R2C=O
Carboxylic acids R-CO2H
Esters R-CO2R'
Amides R-CONR2'
C-NO2
C-F C-Cl
C-Br
C-I
C-H Saturated Hydrocarbons
C-NH2
C-OH C-SR
C-OR C-Ar
C-SO2 R
C-CO R
C-C=C
C CR
RC N
Heteroaromatics
Aromatics
R2C=CH2
RHC=CHR
R2C=CH2
200 150 100 50 0.0
ppm(δ)
Alkenes
Alkynes
1
JCH depends on the bond order ( hybridization ⇔
s-character )
-C-H 1JCH ≈ 125 Hz
=C-H 1JCH ≈ 160 Hz
≡C-H 1JCH ≈ 250 Hz
X-C-H
X = N, O, S, F, Cl, . . . 1
JCH ⇑
X = Li, Mg, . . . 1
JCH ⇓
2
JCH < 0 or close to zero (<3 Hz)
often not observable
Values of chemical shift of important solvents
Abbr. Formula 1
H 13
C
ACN CH3CN 1.9 118
Benzene C6H6 7.2 128
CHCl3 7.2 77
DCM CH2Cl2 5.3 54
DMF (CH3)2NCHO 2.9, 8.0 32, 163
DMSO (CH3)2SO 2.5 40
MeOH CH3OH 3.3, 4.8 49
Water H2O 4.8 Effect
of solvent on the position of residual 1H water signal:
CHCl3 - 1.6, ACN - 2.1, DMSO - 3.3, MeOH - 4.9
How many 13
C signal would you expect in the NMR
spectrum?
Ru
N
N
N
N
Cl Cl
Cl
S CH3
CH3
O
N+
-
N
H
How many 13
C signal would you expect in the NMR
spectrum? 6
Ru
N
N
N
N
Cl Cl
Cl
S CH3
CH3
O
N+
-
N
H
Assign correct value of chemical shift to labelled NMR
active atoms1
:
1
http://www.chem.wisc.edu/areas/reich/chem605/
Assign correct value of chemical shift to labelled NMR
active atoms1
:
1
http://www.chem.wisc.edu/areas/reich/chem605/
Draw the estimate of 13
C NMR spectrum (with and
without 1
H decoupling):
Draw the estimate of 13
C NMR spectrum (with and
without 1
H decoupling):
1D 13
C-NMR 1
1D 13
C-NMR 1
Notes:
C1+C7 connected to
electronegative groups
(C1 quaternary)
C2 ipso aromatic, C4+C6
shielded by M+ of OH
C5+C4 NOE-enhanced in
bit larger extend by close
H
C9→C12: decaying effect
of N8
1D 13
C-NMR 2
1D 13
C-NMR 2
Notes:
C7 carbonyl, C1 attached
to N
C3/5 deshielded by MCO,
C2/6 shielded by M+
of NH2
C4 last quaternary
aromatic signal
C9 effect of esteric group,
? C10 affected by NH
exchange
C12/C14 + C13/C15
decaying effect of N+
1D 13
C-NMR 3
1D 13
C-NMR 3
Notes:
C3/C4 quaternary
aromatic deshielded by O,
Cβ quaternary coupled by
CH3 and CαH
Cα deshielded by NO2
C1 last quaternary
aromatic signal
C2/C6 coupled mutually
and with Cα, C5 isolated
(contraintuitive)
quartets OMe, Cγ
Next topic
Vector model and APT experiment